You're right, military enrollment is not inherently and always coercive; many countries have volunteer-only armies.

For purposes of scaring people with an analogy for "entitlement" rape, we can use the following scenario: your worst enemy, who looks a little like you when he wears a wig, has signed an 8 year irrevocable combat unit contract in your name. It "only looks like" your signature? Tell that to the military police kicking down your door...